Yes, it requires the 'gobjc' package. That's enough for me to compile .m files, but I don't know if 'libobjc2' contains everything an obj-C program could want, or whether you need GNUStep too; I've only ever used it on OS X.

Anyway, it seems that the only hurdle for supporting obj-C is writing a starter package?

You don't have to have GNUStep - that provides all the NS* objects (like NSString, NSValue, NSDictionary, NSArray, NSSet, etc.), but you can write Objective-C code without all that stuff. I guess that would be the first question - can GNUStep be installed on the game servers or not? Then we know if a starter bot should use NS* classes or be written in pure obj-c.